Frye FONIX 7000 - Manual (Page 65)

Basic Sound Chamber Tests
57
4. Signal type, speech weighting, leveling status, and bias status (Digital
Speech only).
5. Selected noise reduction.
6. Source Signal Statistics Box. Displays the source amplitude.
3.2 The Leveling Process
Leveling is the process by which the response of the sound chamber is mea-
sured and computer-corrected so that a “flat” sound field is achieved. The level-
ing status can be saved into the 7000 test system’s permanent memory so that
you don’t have to level the analyzer every time you turn it on. However, if you
get your analyzer calibrated, or if you get a software upgrade, you should always
level the chamber again (and save the leveling).
To double-check the leveling status of the analyzer, place the microphone in the
sound chamber at the reference point by itself and run a composite frequency
response (see Section 3.4.2). You should get a smooth, flat curve.
If you are getting bad coupler frequency responses that you suspect are the fault
of the analyzer, rather than the fault of the hearing aid, the first step of trouble-
shooting is to level the sound chamber. Even if the screen says LEVELED, the
response of the measurement microphone may have altered since the analyzer
was last leveled, invalidating the leveling. When in doubt, level the sound
chamber again.
See Section 2.8 for details on the leveling status and troubleshooting the level-
ing process.
3.2.1 Leveling the sound chamber
To level the sound chamber:
1. IMPORTANT: Be sure nothing is plugged into the battery voltage supply.
2. Place the microphone on the left side of the sound chamber, with the micro-
phone grill over the reference point (Figure 3.2.1). Close and latch the sound
chamber lid.
Warning: Leveling is valid only when the microphone position is not
changed after leveling. Each significant change in microphone location
requires new leveling.
3. Press [F1] to enter the Coupler screen.
4. Press [LEVEL] to start the leveling sequence. The system responds by pre-
senting a complex composite signal consisting of tones from 100 to 8000 Hz.
It measures the signal and stores correction factors, so that the sound field is
flat for testing.
5. Look at the display. After a few seconds, the video monitor should display a
“Leveled” message under the Curve Characteristics box. If the 7000 doesn’t
level, it could be an indication that your microphone needs to be calibrated
or replaced.